Option variable
listdummyvarsDefault value: true
When listdummyvars is false, "dummy variables" in the
expression will not be included in the list returned by listofvars.
(The meaning of "dummy variables" is as given in freeof.
"Dummy variables" are mathematical things like the index of a sum or
product, the limit variable, and the definite integration variable.)
Example:
(%i1) listdummyvars: true$ (%i2) listofvars ('sum(f(i), i, 0, n)); (%o2) [i, n] (%i3) listdummyvars: false$ (%i4) listofvars ('sum(f(i), i, 0, n)); (%o4) [n]